Same SGC 7 Mantle Sold 4 times in 15 months

[Snowman]

All of what you said is certainly plausible. But there are numerous other scenarios that are just as plausible, if not perhaps more likely.

As someone who deals with data for a living, it is often helpful to pretend that certain data points that came from a period of time where something extraordinary happened just didn't actually happen. At least when making projections about the future is the goal. As an example, if I were tasked with building a model to predict the hammer prices of future 52 Mantles at auction, I would overwrite all sales data from at least the first half of 2021, and use values that were projected through that time period instead, as something definitely happened that caused the market to spike artificially and then quickly return back to earth. I've had to do this numerous times when building models in the medical industry with respect to COVID data.

As you can see from the CL50 Index plot below (Card Ladder's 50 most "important" cards in the hobby index), there was a massive spike right around that time. The peak of this plot is on March 7, 2021. That Mantle SGC 7 sale of $550k was on March 11, 2021. So it easily could have been a valid sale where some poor sucker just lost his pants.

Cliff Notes: I would ignore that $550k data point. It may or may not have happened, but the fact that it is an outlier does not indicate that it is necessarily a fake sale. It is more helpful to disregard sales from this narrow window of time if trying to draw conclusions about long-term trends in the market.

Unless, of course, your goal is to try to figure out what happened during those few months, which I would argue is a completely different conversation (or perhaps this is precisely the conversation you're trying to have here... in which case, I'm all ears lol)

..